\tikzstyle{commonbox}=[rectangle, draw=black, rounded corners, text centered,
	anchor=north]
\tikzstyle{graybox}=[commonbox, fill=Gray!20]
\tikzstyle{shadowbox}=[commonbox, drop shadow]
\tikzstyle{greenbox}=[shadowbox, fill=YellowGreen!50]
\tikzstyle{apribox}=[shadowbox, fill=Apricot!50]
\tikzstyle{bluebox}=[shadowbox, fill=CornflowerBlue!50]
\tikzstyle{redbox}=[shadowbox, fill=Red!50]
\tikzstyle{blackbox}=[shadowbox, fill=Black!65, text=White]
\tikzstyle{arrow}=[->, thick]
\tikzstyle{vecarrow}=[thick, decoration={markings,mark=at position
	1 with {\arrow[semithick]{open triangle 60}}},
	double distance=1.4pt, shorten >= 5.5pt,
	preaction={decorate},
	postaction={draw, line width=1.4pt, white,shorten >= 4.5pt}]
